Half-tone high-light process



Patented Mar. 5, 1946 HALF-TONE HIGH-LIGHT PROCESS Burtt-L. Berry, San Francisco, Calif., asslgnor to Burtt L. Berry, Victor-ville, Calif., and Lyle P. Youn'gdahl, San Francisco, Calll'.

No Drawing, Application July 2, 1941, I Serial No. 400,826

(Cl. 95-5) I 4 be those just beyond either end of the visible solar 18 Claims.

improvement in such methods of producing dropout high-light half tone screen negatives in which th high-light dots are entirely or substantially closed on the negative by overexposure of the v high-light areas of the copy, and the invention is based on my discovery that the high-light areas of anycopy to be reproduced by the half tone screen process may be surface treated by a fluorescent substance so that by proper illumination or irradiation they will give off an actinic light to close the high-light dots on the photographic plate or film in the camera while the remainder of the copy including high-light areas not treated will be non-luminous or inactive.

Briefly described my invention comprises applying to such high-light areas of the copy as are de-. sired to'be pure white or free of dots in the final print or cut, a coating or wash which will leave over such areas a finely divided layer of a fluorescent material of a type adapted to emit a photographically actinic ray upon irradiation, preferably by an invisible or substantially invisible ray such as by ultra violet light, so that after normal exposure of the plate or film in the half tone. screen camera to the copy illuminated by daylight, are light, or other electric light, the normal source spectrum directed against the copy with highlights coated with a layer of any suitable fluorescent substance which will emit an actinic light under the activating action of the rays; or, in i act, the irradiation may be by cathode or X rays and th fluorescent material may be barium sulphate, or zinc sulphide copper activated and dampened with nickel, as used'for fiuoroscopes, or other substance adapted to be activated into luminosity by these rays, and in such case there wouldbe no actinic reflection from thesurrounding areas of the copy during the closing-in exposure. The same would be true if infra red rays were used.

However, as it is more convenient to usea band of rays from the ultra violet end of the spectrum for the irradiation of the high-light areas, preferably a band of ultra violet oi from 4000 to 4200 Ang. (or more practically including wave lengths from about 3500 to about 4500 Ang.), there will be some actinic reflection of these rays from the general surface of thecopy which was not treated certainty. I I If violet or ultra violet rays are usedfor the irradiation, they may be obtained from any special of illumination is shut oil and an irradiating ray I is directed against the copy tocause the treated high-light areas, to fiuoresceand give off a strongly actinic light which will continue to impress the plate over such areas only and close upthe hi h-light dots. I

The irradiating exposure-may be made before the normal exposure if desired and the result will be substantially the same; also a large closing-in diaphragm or stop should be used on the lens, as the remaining parts of the copy not being treated are non-luminous during the irradiating expo-sure.

The irradiation of the copy for fiuorescing the treated high-light areasis preferably done with rays totally invisible or yielding no actinic reflection from any part of an ordinary photoengravers copy such as an artists wash drawing, pen drawing, photograph, or other copy, so that the fluorescent high-lights alone will continue to impress the with the fluorescent material, and with the use of such rays, or even slightly more visible rays, it is an advantage, and in some cases necessary to use a color filter over or behind the lens of a color to stop such reflected rays so that the rest of the photographic plate will not be afiected during the closing-in exposure.

It is possible to make allowances for such additional efiect from such violet reflection, by

shortening the'normal exposure of the negative to white light, but this brings in an element of unlamp generating these rays and directed to the copy after the electric lamp for regular illumination has been turned off, or if an electric arc lamp or other lamp rich in ultra violet rays is used for the regular illumination of the copy, as soon as the regular exposure is finished, a suitably colored filter may be placed between the same light source and the copy to permit the continued passage of the irradiating rays to the copy while shutting off the balance of the light. Of course care is taken to have the room dark and avoid any wall reflections of any of thebalance of the light of the lamp or from other sources,to any appreciable extent.

In considering fluorescent materials for the fact that the words fluorescent, luminescent,

plate in the closing-in exposure. Such rays could phosphorescent and photo-phosphorescent, are

the purpose of this invention, attention is called to not clearly defined but appear generally to have overlapping meanings-but as used herein the word fluorescent means such materials as will emit an actinic light when irradiated with an invisible radiation or more or less visible radiation, though such materials may also be photo-phosphorescent-that is, capable of giving oil light after irradiation has ceased, and frequently after exposure to ordinary or white light. Thus if a layer or coating of a chemical or material which is simply photo-phosphorescent, be applied to the high-light areas of the copy and be illuminated by daylight or electric or arc light, and the light turned off, the resulting continued phosphorescent glow of the treated areas may alone be sufllcient to close in the high-light dots over such treated areas. Besides, to be considered is that even during the illumination of the copy by such ordinary light, it is probable that the treated high-light areas are in fact by combined reflection and photo-phosphorescent glow, acting much more strongly on the high-light dots than anyuntreated areas and are thereby hastening the closling-in action during the regular exposure.

Where a chemical or material is used for treating the high-light areas which is both photophosphorescent as well as fluorescent to invisible radiation or substantially invisible radiation, or to deep violet radiation, the subsequent irradiation of the treated copy after the normal exposure will intensify the light emitted from the high-light areas or maintain it at a high state of activity for any desired length of time, but where the treating chemical or material is only fluorescent to invisible radiation it may nevertheless be equally effective to close in the high-light dots, as this depends on the eficiency of the material, the thickness of the coating, and the power Or strength of the irradiating rays. Therefore in my appended claims, unless otherwise qualified the language is intended to cover activating material having any or all of the above explained properties.

In making the closing-in exposure, in addition to the use of a large stop'in the lens, the half tone screen may be moved further from the plate, or swung away or removed entirely from in front of the plate if the construction of the camera permits, to thereby hasten or more completely effect the closing-in exposure.

Besides the fluorescent materials mentioned may be the luminescent or fluorescent grades of sulphides of calcium, strontium, barium, and zinc generally combined with a minute quantity of bismuth or thorium oxide. The quality of such materials generally known in trade as fluorescent grade" has been found' to give good results. Other substances such as anthracene, eosine, also thioflavine are useful as they are fluorescent under ultraviolet rays of from 3500 to 4500 Ang. without being photo-phosphorescent. Mixtures of the above materials may be used.

In using the fluorescent materials for the purpose of my invention they are very finely ground up and mixed with an adhesive liquid to form a paste or paint which is applied to the highlights of the picture or copy with a brush, or sprayed on if the areas are large. The outlines or edges of the areas may be left sharp or abrupt or they may be blended gradually into the adjacent areas as may be desired. A satisfactory vehicle is equal quantities of a 5 or 6% aqueous solution of gelatine and a 20% aqueous solution of gum arabic, to which mixture is added about 50% by weight of the fluorescent material, thoroughly mixed, say anthracene, as it gives a pale yellow tint where applied to the high-lights so that its outline maybe seen and blending effects may be followed. The fluorescent light is a greenish white.

Another good vehicle or binder is a weak aqueous solution of shellac cut with ammonia.

Another way of applying the powdered fluorescent material is to first paint the desired areas with a slightly tacky solution, or varnish, then dust the material over these areas and brush off all loose particles from adjacent areas.

When ultraviolet rays are used in'irradiating the fluorescent areas, the use of a color filter before the lens to absorb any ultraviolet which may be reflected from the copy. may be dispensed with by suitable preparation of the whole surface of the artist's board or paper before making the drawing so as to absorb such irradiating rays, and over which the drawing or copy is-made. A suitable material for this purpose is the aniline dye known as water soluble Brilliant Green and/ or soluble Brilliant Blue, or mixture of these. A'5% aqueous solution of this together with sufllcient of the gelatine-gum arabic binder to hold it to the paper has been found satisfactory. The surface of the paper may be coated by air brush, wet roller, floating, or careful brushing, or the absorbent may be incorporated throughout the substance of the paper of the drawing at the time of manufacture of the paper, or by any other method. When dry it may be worked over with water color or ink in the ordinary manner, and the fluorescent material may be applied directly over it where desired to have a dotless highlight, but to make the overcoating of fluorescent material more effective the under coat or substratum of ultravioletabsorbent may first be 40 locally washed out,'rubbed off with a sand eraser,

or neutralized, as by a chlorine bleaching solution. i

As a modification, such a violet ray absorbent may be mixed with the black paint used by the artist in making up his washes, instead of, or together with the absorbent substratum above described. .In this case either the Brilliant Green dye above mentioned or the water soluble dye known as-Saffronine Red may be used, or preferably equal mixtures of both added about 10% to the black water color, such for instance as Windsorand Newton's lamp black water color, and thoroughly incorporated therewith and used in the regular manner for shades and washes in making the drawing. or course, if an irradiating ray is used which has no actinic reflecting power on-the surrounding wash drawing or paper uponwhich it is made, such as the X-ray or cathode ray or invisible ultraviolet or infrared ray, no absorbent substratum nor absorbent in the water color wash, nor ray filter over the lens, need be used, as the irradiation on a suitable fluorescent material applied tothe highlights of the picture or copy will cause these areas only. to be luminescent in the closing in exposure.

I might mention in this connection that while the application of the process. to plain photographs is evident as their high-lights need merely be painted in Or sprayed with the preferred fluorescent material, nevertheless I have also found that it such a plain photograph, preferably on mat surface paper, be merely soaked in a thin liquid solution or suspension of the fluorescent material so as to produce an even coataccuses ing in the whole surface and dried; such a treated photograph while manifestly having the fluorescent material over its whole surface, still will be much more luminous in the high-lights when irradiated, tor the reason that much or the fluorescent quality penetrates in and is lost in the darker portions or the photograph, and therefore the high-lights will be illuminated so much more strongly as to afiect to a great extent the closing in of the high-light dots under the general process described above. A suitablefluorescent wash tor thepurpose would be a thin solution or white shellac in alcohol and carrying about of anthracene.

From a consideration of the preceding description of the invention, it will be seen that its purpose is'to produce a half tone screen negative of any desired copy and in which negative the dot structure in any desired high-light areas may be substantially or completely closed to produce a dotless high-light. Such negatives of course may be used for the various half tone methods of printing, such as the making of ordinary half tone cuts therefrom or the use of the negative in making photolithographs or photolithographic transfers in the well known way. However when the negatives are used for making etched cuts on sheet metal, it is evident that in the shallow half tone etching on copper suchareas would require routing out, though with the four way dusting method as applied to zinc etching and particularly with coarse screen efiects as used in newspaper cuts, sufllcient depth of etching may be obtained so that routing will be dispensed with in all except the larger areas.

Having thus described my invention and some of the modifications of it, what I claim is:

l. The method of producing half tone screen negatives with closed in dots in the high-light areas for drop-out high-light cuts and prints,

which comprises treating the high-light areasof the-photoengravers-copy with a fluorescent material adapted to emit an actinic light on said areas, photographing the copy through a photoengravers halitone screen in the ordinary way and using the light emitted from the'fluorescent covered high-light areas forclosing in the highlight dots on the screen negative by prolonged exposure of said areas.

2. The method of producing halt tone screen negatives with closed in dots in the high-light areas for drop-out high-light cuts and prints, which comprises-treating the high-light areas only of the photoengravers copy with a fluorescent material adapted to emit an actinic light-on said areas, making the exposure by ordinary light through a photoengravers half-tone-screen, irradiating thei c'op'y, and using the visible light emitted from-@the fluorescent material on the high-lights forclos'ing in the high-light dots on theiscreen negative'by prolonged exposure of said areaa- 1 3. The method of producing half tone screen 1 negatives with closed in dots in the high-lightareas for-drop out high-light cuts and prints,

saidareas when irradiated with an invisible ray,

. I illuminating the copy by substantially white 11cm;

tone screen negative, shutting out said white light and irradiating the copy with a substantially innegatives as set out in claim 4 wherein the irradiating ray is ultra violet.

visible my to cause the treated high-light areas to fluoresce, and using the visible light so emitted from the high-light areas for closing in the highlight dots on the screen negative by prolonged exposure of said areas. I

4. The method of producing half tone screen negatives withclosed in dots in the high-light areas for drop-out high-light cuts and prints, which comprises treating thi hi hlight areas only oi. the photoengravers copy with a fluorescent material adapted to emit an actinic light on said areas when irradiated with a substantially invisible ray, illuminating the copy by substantially white light and making the regular exposure through a photoengrave'rs half-tone screen to form the half tone screen negative, shutting out said white light and irradiating the copy with a substantially invisible ray to cause the treated high-light areas to fluoresce, and using the visible light so emitted for closing in the high-light .dots on the screen negative by prolonged exposure or said areas while filtering from access to the sensitive plate any actinic reflection or said substantially invisible ray from said copy.

5. The method of producing halt tone screen 6. The method of producing half tone screen negatives as set out in claim 4 wherein the irradiating ray is an ultra violet band extending from about 3500 to 4500 A118.

7. In the method or producing half tone screen negatives as set out in claim 1 wherein the fluorescent material is also photo-phosphorescent.

8. In the method oi producing halt tone screen negatives as set out in claim 4 wherein the fluorescent material is also photo-phosphorescent.

9. In the method of producing half tone screen negatives as set out in claim 3 wherein the ir- 40 radiating ray is cathodic or the x ray.

10. In a method of producing half tone screen negativesas set out in claim 3, providing the copy with a substratum of an absorbent or the irradiating ray wave length so as to prevent reflection of said ray from saidcopy to the negative during irradiating exposure.

11. In the method of producing halt tone screen negatives as set out in claim 3, the use of an absorbent of the irradiating wave length incorporated in the shading material or which the copy is formed. a

12. In the method of producing halt tone screen negatives as set out in claim 1, the fluorescent material being finely divided andmixed with a binder adapting it to be painted or sprayed on the areas desired.

13. In the method of producing half tone screen negatives as set out in claim 1, the fluorescent material being liquid soluble and iorniedinto a to be painted or sprayed on the areas desired.

14. In the method of producing, halt tone screen I negatives as set out in claim 1, the fluorescent which comprises treating the high-light areas only of the photoeng'ravers copy with a fluorescent material' adapted to emit an actinic light on material being'liquid soluble and termed into a solution with a liquid and the entire copy treated on its surface with said solution. I

15. The method of claim 1 wherein the fluorescent material is photo-phosphorescent and the after glow from the regular illumination of the I copy in making the half tone screen negative is used to close up the high-light dots after the regular source of illumination of the copy has which is also photo-phosphorescent adapted when excited to emit an .actinic ll'xht.

18. Copy for the drop-out iah-lisht halt tone process characterized in having its high-light areas only coated with a pinto-phosphorescent material.

BURTT L. BERRY. 

